Kerberoasting
Service principal names (SPNs) are used to uniquely identify each instance of a Windows service. To enable authentication, Kerberos requires that SPNs be associated with at least one service logon account (an account specifically tasked with running a service (Citation: Microsoft Detecting Kerberoasting Feb 2018)). (Citation: Microsoft SPN) (Citation: Microsoft SetSPN) (Citation: SANS Attacking Kerberos Nov 2014) (Citation: Harmj0y Kerberoast Nov 2016) Adversaries possessing a valid Kerberos ticket-granting ticket (TGT) may request one or more Kerberos ticket-granting service (TGS) service tickets for any SPN from a domain controller (DC). (Citation: Empire InvokeKerberoast Oct 2016) (Citation: AdSecurity Cracking Kerberos Dec 2015) Portions of these tickets may be encrypted with the RC4 algorithm, meaning the Kerberos 5 TGS-REP etype 23 hash of the service account associated with the SPN is used as the private key and is thus vulnerable to offline Brute Force attacks that may expose plaintext credentials. (Citation: AdSecurity Cracking Kerberos Dec 2015) (Citation: Empire InvokeKerberoast Oct 2016) (Citation: Harmj0y Kerberoast Nov 2016) This same attack could be executed using service tickets captured from network traffic. (Citation: AdSecurity Cracking Kerberos Dec 2015) Cracked hashes may enable Persistence, Privilege Escalation, and Lateral Movement via access to Valid Accounts. (Citation: SANS Attacking Kerberos Nov 2014)
Mitigations |
|
| Mitigation | Description |
|---|---|
| Privileged Account Management |
Manage the creation, modification, use, and permissions associated to privileged accounts, including SYSTEM and root. |
| Kerberoasting Mitigation |
Ensure strong password length (ideally 25+ characters) and complexity for service accounts and that these passwords periodically expire. (Citation: AdSecurity Cracking Kerberos Dec 2015) Also consider using Group Managed Service Accounts or another third party product such as password vaulting. (Citation: AdSecurity Cracking Kerberos Dec 2015) Limit service accounts to minimal required privileges, including membership in privileged groups such as Domain Administrators. (Citation: AdSecurity Cracking Kerberos Dec 2015) Enable AES Kerberos encryption (or another stronger encryption algorithm), rather than RC4, where possible. (Citation: AdSecurity Cracking Kerberos Dec 2015) |
| Encrypt Sensitive Information |
Protect sensitive information with strong encryption. |
| Password Policies |
Set and enforce secure password policies for accounts. |
Detection
Enable Audit Kerberos Service Ticket Operations to log Kerberos TGS service ticket requests. Particularly investigate irregular patterns of activity (ex: accounts making numerous requests, Event ID 4769, within a small time frame, especially if they also request RC4 encryption [Type 0x17]). (Citation: Microsoft Detecting Kerberoasting Feb 2018) (Citation: AdSecurity Cracking Kerberos Dec 2015)
References
- Metcalf, S. (2015, December 31). Cracking Kerberos TGS Tickets Using Kerberoast – Exploiting Kerberos to Compromise the Active Directory Domain. Retrieved March 22, 2018.
- EmpireProject. (2016, October 31). Invoke-Kerberoast.ps1. Retrieved March 22, 2018.
- Schroeder, W. (2016, November 1). Kerberoasting Without Mimikatz. Retrieved March 23, 2018.
- Medin, T. (2014, November). Attacking Kerberos - Kicking the Guard Dog of Hades. Retrieved March 22, 2018.
- Microsoft. (2010, April 13). Service Principal Names (SPNs) SetSPN Syntax (Setspn.exe). Retrieved March 22, 2018.
- Microsoft. (n.d.). Service Principal Names. Retrieved March 22, 2018.
- Bani, M. (2018, February 23). Detecting Kerberoasting activity using Azure Security Center. Retrieved March 23, 2018.
Связанные риски
Каталоги
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